Fuel duration meter



Oct. 21, 1952 v. E. PAYNE 2,614,422

FUEL DURATION METER Filed Jan. 6, 1949 IN V UV TOR. Uiron E. Payne BY MWPatented a. 21, 1952 UNITE-D srArss PATE T OFFICE This invention isdirected to, and it isan object to provide; an instrument which isoperative to indicate to the operator of 'an'eng ineusing liquid" fuelftheamountof time-4n terms of hours and minutes-' which the engine willcontinue to run' ontheifuel'remainingin the supply tank.

*Wh'ile" the instrument adaptable to' "sundry types of'liq'uid fuelfactuated e'ngines, the inventibnis-designe'd primarily'for aircraftuse. Another objectbf'the 'inventio'nisto provide a fuel" durationinstrument which is self-compensatingwithrespectto'variations'in therate of fuel consumption; to-wit; if the engine speed or'load,

or both; is iiicreas'edfor-decreasecl' with resultant increase-or]decrease? respectively, in fuel con-" sumption, the instrumentwil1"automatically re-" flect an'a'dju'sted proportionately lesserorgreater rernainir' gperiod "of engine operation.

'A further object of "the invention is'to provide;

affuel durationinstrument which is continuously operative to indicate,on a constantly adjusted" basis as above; the remaining period of engineoperation at'thespeed*-and load thereof when any'rea'ding is taken; Thisis a very advantageous feature, especially in connection with theoperation of aircraft.

An additionalobject'of the invention is to pro:- vid? a fuelduration-instrument,for the purpose described, which functions uponthe'principle of dividing fuel; quantity by ratelofjconsumption todetermineduration of operation. This is accomplished,iautomatically, in"the present embodiment by the division ofc'urrent' between parallelimpedance'circuitsfthe impedance of one cir'cui't being variableinres'po'nse'ftd change in, and cor responding to; therate gffuelcgrisumptio'ri; the impedance of the 'other-circui-t being variablein Calif fitted With'a device responffuelremainingin the tank creaseofthe rate offlow of fuel through-the-pi-pe 2, the device l actuates thevariable impedance 6 to a proportionate extent, and in a direction toincrease the impedance. Similarly, upon reduction in the quantity offuel in the tank 3, the de vice or float 4 actuates the variableimpedancefi to a proportionate xtent, and

in a direction-t0. reduce the impedance; 4 a

The numeral-9 includes an input circuit whichleads to connection withparallel-wired imped ance circuits; one being indicated at-IIJ and theother-at-I-L r response,;-and corresponding to. the amount-of;

M 11 t :tanla are. a l el qtria n zwscale to re'adin terms of hours andminutes of fuel duration-is arranged in connection with said circuits ina manner to reflect the division of current therebetween so as tocontinuously give an accurate reading of the remainingperiod of engineoperation.

A further object of the invention is to provide a practical and reliablefuel duration instrument,'and one which will be exceedingly effectivefor the purpose for which it is designed.

These objects are accomplished by means of such structure and relativearrangement of parts as will fully appear by a perusal of the followingspecification and claims.

The figure of the drawing is a diagrammatic illustration of a preferredform of circuit for the instrument.

all times, and as is necessary tio n th nstrumen -Mt Y The variableimpedance 6 is interposed inthef circuit 10, while the variableimpedance8 isin- .terposed in the circuit,

A current regulator I2 is connectedin the;in-" putcircuit 9 ahead of theparallel-wired, impede ance circuits; I0 and I I, .to the end that theCD1 1;

rent supplied tocircuits I0 and isconstant "aztto pr per .funce,

. An electric meter I3 is interposed either lead of thejmpedancecircuit;vsuch meter t3.

e udi a movable nd Iiwliichreadson; adial,

I5 scaled in terms of hours and minutes.

The impedance circuit I0, including the variable impedance 6, may betermed the rate of flow or consumption sensing circuit, while theimpedance circuit I I, including the variable impedance 8, may be termedthe fuel quantity sensing circuit.

The instrument functions by the division of current between the circuitsIn and I I as reflected by the meter I3 in terms of fuel duration. Suchfunction will be clearly understood from the following formula whereinthe impedance of the circuits I0 and I I is represented by Z1, and Z2,the total impedance in the system by Z, and the current in said circuitsrepresented by I1 and I2. The total current is I0 and is the vector sumof the currents flowing in the two parallel circuits. The

3 letter V represents the voltage drop across said two parallel circuitsdue to the passage of the current Io. The following equations then showthe relationship between the various quantities:

IoZz/(Zr-l-Zz) If the rate of fuel consumption of the engine is made toequal 21/ K1 and the total fuel remain- Now D equals 62/15, 50 F/Qequals l/D. Substituting gives:

In thefinal equation shown above, the duration is shown to be given bythe relation between two variables multiplied by the ratio of the twoconstants.

It will be seen that there is no theoretical restriction placed on thetype of impedances used, as long as the values of the impedances arevaried in accordance with the rule given.

It is thus evident that the instrument described herein will indicate,Within relatively accurate limits, the remaining duration of engineoperation, at the existing rate of fuel consumption and with the amountof fuel remaining, at the timed check.

It is to'be-understood-that for any particular adaptation of theinstrument, and its circuit as in the figure'of" the drawing,thevariable impedances 6 and 8, the rate of flow'device I, the meter l3,and the current regulator I2 will be of predetermined capacity andsuitably normally balanced relative to each other;

From the foregoing description it will be readily seen that there hasbeen produced such a device as substantially fulfills the objects of theinvention as set forth herein.

While this specification sets forth in detail the present and preferredconstruction of the device, still in practice such deviations from suchdetail may be. resorted to as do not form a departure from the spirit ofthe invention, as defined by the appended claims.

Having thus described the invention, the following is claimed as new anduseful, and upon which Letters Patent are desired:

1. An instrument for indicating fuel "duration for an engine fed from atank having a quantity of fuel therein, comprising means responsive tothe ratev offlow of fuel feedin between the engine and tank, meansresponsive to the amount of fuel remaining in the tank, separatevariable impedances mechanically linked to the means responsive to therate of fuel flow and to the means responsive to the amount of fuelremaining in the tank for actuation thereby, a separate circuit in whicheach impedance is interposed, said circuits being connected in parallel,means to supply a constant current to said parallel circuits, and acurrent meter interposed in one of said circuits operative to reflectthe division of current thereb-etween, said current meter beingcalibrated in terms of fuel duration; there being an input circuitconnected to said parallel circuits, and said constant circuit supplymeans including a current regulator in the input circuit.

2. An instrument for indicating fuel duration for an engine fed fromatank having a quantity of .fueltherein, comprising a pair of separateimpedance circuits each including a variable'impeda'nce, said circuitsbeing connected in parallel, means to feed a constant current to saidparallel circuits, a current meter in one of said circuits, said meterbeing calibrated in terms of fuel duration, means operative to vary oneimpedance in response to the rate of fuel consumption by the engine, andmeans including a fuel level float to vary the other impedance inresponse to the amount of fuel remaining in the tank.

VIRON E. PAYNE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,533,530 Wheatley et al. Apr.14, 1925 1,655,276 'Lichtscheindl Jan. 3, 1928 2,169,048 Howe et al.Aug. 8, 1939 2,500,585 Sylvander Mar. 4, 1950v FOREIGN PATENTS NumberCountry Date 819,460 France July 12, 1937

